Petz (Prizma in the English versions) is the oldest of the four sisters, with the magical power called "Dark thunder" in the anime, though she is only shown using a tornado in the manga, paralleling Sailor Jupiter's Flower Hurricane. She is named for the mineral petzite and is the counterpart of Makoto Kino.

In the manga, Petz is assigned "Code003 Operation Re-new" and she and her UFO release viruses onto Tokyo to infect the population. Makoto is infected by one of the viruses and passes out in her apartment. She awakens to her double trying to choke her, and she transforms and attacks it as Sailor Jupiter, revealing it to be a droid. Petz then arrives in her UFO, expresses amusement that Jupiter is still alive, then swears vengeance for her two dead sisters. She and Jupiter fight, but Petz captures her inside of a tornado she summons using the Black Crystal. Petz watches Jupiter in the tornado and does not see the arrival of Sailor Moon and Sailor Venus, and she is killed from behind by Moon Princess Halation, though Rubeus still succeeds in kidnapping Jupiter.

In the anime, Petz often clashes with Calaveras, but the majority of both women's operations end up with them working together. She is very proud and is willing to step on others to achieve personal glory and power. She also appears bitter over a past relationship and reacts strongly when Calaveras teases her about it. After the betrayal of Cooan and Berthier, Rubeus gives her a stick that will infinitely increase her dark powers and instructs her to use it to kill both the Sailor Senshi and her fallen sisters. He also warns her that if she fails, she will not be allowed to return. The stick dramatically increases Petz' powers and also corrupts her personality, allowing her to quickly gain the upper hand against the Sailor Senshi. She then turns on Calaveras and tries to kill her along with the other two sisters. However, the Senshi regain the advantage and knock the stick away from her, reducing her power again. Rubeus then appears and reveals to Petz that he had actually expected Petz to fail; his goal was not for her to succeed, but to lure the Sailor Senshi out and sacrifice all four sisters to kill them. He then activates the stick's true power and it creates a massive time-vacuum that threatens to pull in everyone around it. Petz, no longer possessed and remorseful, decides that she has enough power in her body to destroy the stick and jumps into the vortex to sacrifice herself to stop it. However, she is stopped by her other three sisters. After the vortex is destroyed by the Sailor Senshi, Petz is purified along with Calaveras.

Later, Petz and her sisters discover a wounded Saphir, whom Petz tends to even though she at first thinks he came to punish her sisters. It is then that Petz and Saphir are revealed to have been romantically involved, therefore Saphir is the person who caused Petz to be embittered about men. After Saphir is killed by Wiseman, Petz senses his death and is heartbroken, but remembers how he smiled for her.